New Lithium Salt Forms Interphases Suppressing Both Li Dendrite and Polysulfide Shuttling

Lithium–sulfur batteries (LSBs) are considered promising candidates for the next-generation energy-storage systems due to their high theoretical capacity and prevalent abundance of sulfur. Their reversible operation, however, encounters challenges from both the anode, where dendritic and dead Li-metal form, and the cathode, where polysulfides dissolve and become parasitic shuttles. Both issues arise from the imperfection of interphases between electrolyte and electrode. Herein, a new lithium salt based on an imide anion with fluorination and unsaturation in its structure is reported, whose interphasial chemistries resolve these issues simultaneously. Lithium 1, 1, 2, 2, 3, 3-hexafluoropropane-1, 3-disulfonimide (LiHFDF) forms highly fluorinated interphases at both anode and cathode surfaces, which effectively suppress formation of Li-dendrites and dissolution/shuttling of polysulfides, and significantly improves the electrochemical reversibility of LSBs. In a broader context, this new Li salt offers a new perspective for diversified beyond Li-ion chemistries that rely on a Li-metal anode and active cathode materials.